O-(alpha-hydroxycinnamoyl)benzoic acid and related compounds

ABSTRACT

A NOVEL CLASS OF REAGENTS REACT WITH PRIMARY AMINECONTAINING COMPOUNDS, PREFERABLY POLYPEPTIDES AND AMINO ACIDS, TO FORM HIGHLY FLUORESCENT PRODUCTS. THIS REACTION SERVES AS A BASIS FOR A RAPID AND HIGHLY SENSITIVE ASSAY METHOD FRO PRIMARY AMINE-CONTAINING COMPOUNDS.

United States Patent Office 3,812,181 Patented May 21, 1974 ABSTRACT OF THE DISCLOSURE A novel class of reagents react with primary aminecontaining compounds, preferably polypeptides and amino acids, to form highly fluorescent products. This reaction serves as a basis for a rapid and highly sensitive assay method for primary amine-containing compounds.

BACKGROUND OF THE INVENTION The use of ninhydrin as a colorimetric reagent for the detection and assay of amino acids, amines and peptides has been known in the art for nearly 60 years. It serves as the basis for the well known Stein-Moore procedure now extensively utilized in the automated assay of amino acids. McCaman and Robins described a lluorometric method for the detection of serum phenylalanine involving the reaction between ninhydrin and phenylalanine and discovered the fluorescence was greatly enhanced by the addition of a variety of peptides. Later, Udenfriend and coworkers, Anal. Biochem. 42, 222, 237 (1971), described a fiuorometric assay procedure for primary amine-containing compounds, especially peptides and amino acids, which involved the reaction between the primary amine-containing compound, ninhydrin and an aldehyde, preferably phenylacetaldehyde. This procedure was shown to be much more efiicient and sensitive than the Stein-Moore and MaCaman-Robins procedures.

BRIEF DESCRIPTION OF THE INVENTION The present invention relates to a novel series of compounds represented by formula I iji wherein R is hydrogen, halogen, lower alkyl or lower alkoxy and R is lower alkyl or aryl.

matic ring system which may be substituted with one or more of the following: halogen (i.e., fluorine, chlorine, bromine or iodine), lower alkyl, lower alkoxy, nitro, cyano and so forth. Exemplary aromatic ring systems include phenyl, naphthyl, furyl, thienyl, pyrrolyl, imidazolyl, pyridyl, pyrimidinyl, indolyl, quinolyl, oxazolyl, isoxazolyl, and so forth.

Preferred compounds of formula I are those where R is hydrogen. Examples of preferred compounds of formula I are:

4-phenylspiro[furan-2 (3H) ,1'-phthalan]-3,3 '-dione 4- 2-rnethoxyphenyl) spiro [furan-2 3H) 1 -phthalan] 3 ,3 -dione 4- (3-methoxyphenyl) spiro [furan-2(3H),1'-phthalan]- 3,3 '-dione 4- (4-methoxypheny1) spiro [furan-2 (3H) ,1'-phtha1an]- 3 ,3 '-dione 4- (2,4-dimethoxyphenyl)spiro [furan-Z (3H) ,1-

phthalan] -3,3 '-dione 4 2,5 -dimethoxyphenyl) spiro [furan-2( 3H) 1'- phthalan] -3,3'-dione 4- 3,5 -dimethoxyphenyl) spiro [furan-2 3H) 1'- phthalan] -3,3-dione 4- 3,4,5 -trimethoxyphenyl) spiro[furan-2 (3H 1- phthalan] -3 ,3-dione 4- 2,4,5 -trimethoxyphenyl) spiro [f'uran-Z (3H) -1'- phthalan] -3, 3 -dione 4-( 3 ,4-methylenedioxypheny1)spiro [furan-Z 3H) lphthalan] -3 ,3 '-dione 4- (3 -chlorophenyl spiro [furan-Z (3H 1 -phthalan] 3,3-dione 4-g l-chlorophenynspiro[furan-2(3H),1'-phthalan]-3,3'-

lone 4- (t-bromophenyl) spiro [furan-2 3H) 1'-phthalan]-3,3

1one

4- 3-indolyl spiro [furan-2( 3H ,l"-phthalan] -3,3 '-dione 4-(2-naphthyl)spiro [furan-2(3H),.1'-phthalan]-3,3-

dione 4- 1-naphthyl) spiro [furan-Z 3H) ,.1'-phtha1an] -3,3'-

dione 4-( 1-propyl)spiro[furan-2(3H),1'-phtha1an]-3,3-dione.

Especially preferred is the compound wherein R is phenyl, i.e. 4-phenylspiro [furan-'2( 3H ,1-phtha1an] -33- dione.

The preparation of compounds of formula I is illustrated in Reaction Scheme A starting from compound II. Compounds of formula II are generally known and are prepared starting with the properly substituted o-acetyl benzoic acid and the desired aldehyde RCHO. Where particular members of the genus represented by formula II have not been previously described in the art, they may be prepared in the same manner as the known ones.

REACTION SCHEME A COQH O CO H O l R III R Q I on R- I a i I R: 002K 0 n I IV wherein R and R are as above; R and R taken independently are each lower alkyl; and R and R taken together with the nitrogen atom form a 5- or 6-membered saturated heterocyclic ring having at the most one additional heteroatom selected from the group consisting of nitrogen and oxygen.

In the first step, the enol lactone of formula II is bydrolyzed to the keto carboxylic acid of formula III by an aqueous basic hydrolysis, followed by acidification. Suitable bases for the hydrolysis reaction include alkali metal hydroxides, e.g. sodium hydroxide, alkali metal carbonates, e.g. sodium carbonate, and alkali metal bicarbonates, e.g. sodium bicarbonate. A preferred base is an alkali metal hydroxide such as sodium hydroxide. The temperature of the hydrolysis can be in a range of from about 0 to about 100 C. A preferred temperature range is from about 10 to about 40 C. The hydrolysis reaction is suitably performed in an aqueous medium. An organic cosolvent such as a lower alkanol or an organic ether may be employed if desired. At the completion of the reaction, the reaction mixture is acidified to free the carboxylic acid reaction product for the purposes of isolation.

Compounds of formula III are depicted as existing in both the diketo and the enolized form. It should be understood that the ratio of tautomers of the compound can vary depending upon olvent, temperature, pH, and so forth. In the experimental section and the claims, the compounds of formula III are named as the enol form for convenience only.

The keto carboxylic acid of formula III may be converted to the fluorogen of formula I by a two step procedure. In the first step the keto acid of formula III is reacted with an amino-methenylating agent to afford an enamine of formula IV. Suitable aminomethenylating agents include acetals of an N,N-disubstituted formamide, e.g. dimethylformamide dimethylacetal; tris(secondary amino)methanes, e.g. tris(dimethylamino)methane and tris(piperidino)methane; and bis(secondary amino)lower alkoxy methanes, e.g. bis(dirnethylamino)-t-butoxy methane.

The amino moiety as shown in the structural formula for compound IV is introduced from the aminomethenylating agent. Acetals of N,N-disubstituted formamides have the general formula,

tris( secondary amino)methanes have the general formula and bis( secondary amino)lower alkoxymethanes have the general formula Examples of amino moieties include those where R and R each taken independently are lower alkyl, e.g. dimethylamino and diethylamino; and those where R and R taken together with the nitrogen form a 5- or 6-membered heterocyclic ring, e.g. piperidino, morpholino, pyrrolidino, and so forth.

This reaction may be carried out in any inert organic solvent. Particularly preferred solvents include formamides, especially dimethylformamide. An excess of aminomethenylating agent may be also utilized as solvent. The preparation of the enamine may be effectuated over a temperature range of from about 0 to about although a temperature range of from about 10 to about 40 is preferred. A temperature of about room temperature is especially preferred.

The enamine of formula IV may be then directly converted to the fluorogen of formula I by aqueous hydrolysis at a neutral acidic or basic pH. Thus, an acid such as a mineral acid, e.g. HCl; or a weak base such as an alkali metal bicarbonate, e.g. sodium bicarbonate, may be present in the hydrolysis medium. In general, it is preferred to effectuate the aforementioned hydrolysis in the presence of a weak base such as an alkali metal bicarbonate. Upon completion of the hydrolysis and acidification of the reaction medium (in cases Where the hydrolysis is carried out on the neutral or basic side) the desired cyclized fiuorogen of formula I is obtained. The temperature of the hydrolysis reaction is suitably in the range of from about 0 to about 100", although a temperature of about 10 to 40 is preferred. A temperature of about room temperature is especially preferred. The conversion II II I, III-*IV and IV I may be carried out with isolation and purification of the product at each stage or, preferably, can be carried out with isolation and purification only of the final fluorogen of formula I.

The fluorogens of formula I react readily with primary amine-containing compounds, particularly with peptides, amino acids and biogenic amines, e.g. catecholamines, to form highly fluorescent materials. Thus, the compounds of formula I serve as highly sensitive reagents for the detection of primary amine-containing compounds. Since the compounds of formula I are stable to aqueous media, the detection of primary amine-containing compounds present in said media is rendered highly practical. This is especially important for the detection of amino acids and peptides which are generally found and analyzed in aqueous media.

The reaction between fiuorogens of formula I and primary amine-containing compounds is a rapid and quantitative one. The reaction may be carried out over a Wide pH range of from about pH 4 to about pH 11. However, the rate and completeness of the reaction of the fluorogen with the primary amine-containing compounds is optimal within a pH range between about 8 and 9. Thus, reaction of a compound of formula I with a simple primary amine, such as ethylamine, is instantaneously complete at room temperature within this pH range.

(It is immediately apparent that the use of a fluorogenic reagent of formula I for the detection of primary aminecontaining compounds is superior to the prior art technique hereinabove described involving a ternary reaction between a primary amine-containing compound, ninhydrin and phenylacetaldehyde. A further superiority of the reagents and methods of the present invention is seen from the fact that, in the prior art procedure, it was necessary to heat the mixture of reagents to a temperature of about 60 C. for 15 to 30 minutes to develop maximum fluorescence, whereas, in contradistinction, the reagent of the present invention develops maximum fluorescence instantaneously at room temperature. The fluorescence obtained using equal concentrations of primary amine-containing compounds utilizing the reagents of the present invention is generally in the range of to 50 times greater than that obtained by using the prior art technique. Thus, the reagents of the present invention may be utilized to detect exceedingly minute quantities of pri mary amine-containing compounds which was heretofore impossible. Due, to the sensitivity of the reagents of the present invention, small amounts of peptides and amino acids can be detected. For example, one can detect and examine quantities of biologically active peptides isolated from a given organ or a single laboratory animal.

The use of the reagents of the present invention for the detection of primary amine-containing compounds may be illustrated in a number of ways. For example, the presence of primary amine-containing compounds in solution may be determined by mixing the sample with an excess of fluorogen of formula I at a desired pH, and measuring the fluorescence. It is preferred to have the primary amine-containing compound in solution in an aqueous medium and to treat it with a solution of the fluorogen in a non-hydroxylic, water miscible solvent such as acetonitrile, dimethylformamide, dimethylsulfoxide, tetraand the paper or thin-layer chromatogram is examined under a fluorescent light source. The development of fluorescence is instantaneous at room temperature and, thus, there is no need to heat the chromatogram to develop fluorescence. This offers a decided advantage over prior art techniques.

Another application of the fluorogens of the present invention is the use in automated analysis of amino acids. In such a procedure, a sample stream which is a portion of the effluent of a chromatographic column is mixed with the fluorogenic reagent of formula I at the desired pH and the mixture immediately analyzed by a spectrofluorometer. In this manner, a monitoring of the fluorescence exhibited by a continuous sample stream is indicative of the presence and concentration of various amino acids.

A further appreciation of the preparation of the novel fluorogens of the present invention and their use in producing highly fluorescent substances upon reaction with primary amine-containing compounds may be obtained from the following examples.

EXAMPLE 1 A solution of 8.1 g., 1,4-isochromandione (0.05 mole), 6.0 g. benzaldehyde (0.055 mole) and 0.1 ml. piperidine in ml. benzene was heated at reflux temperature under nitrogen until the theoretical amount of water (0.05 mole) had collected in a Dean-Stark trap (ca. 2 hrs.). The reaction mixture was then cooled to 10 and the product was filtered off. The filter cake was recrystallized from benzene to afford 11.4 g., 3-benzylidene-4-keto-3,4-dihydroisocoumarin, M.P. 177.

Analysis.Calcd. for C I-I O C, 76.79; H, 4.03. Found: C. 76.49; H, 4.05.

Analogously were prepared from 1,4-chromandione and the corresponding aldehydes the compounds listed in Table I:

TABLE I O I! Q/Ym.

Analysis Found M.P., Empirical R: degree formula H N 2-methoxyphenyl 200 C11H|1O4 4. 19 3-methoxyphenyl-.- 153 011111204 4. 21 4-methoxyphenyl 200 C11H1z04 4. 29 2,4-dimethoxyphenyl- 201 013111405 4. 57 2,5-dimethoxyphenyl- 160 (313111405 4. 54 3.5-d1meth0xyphenyl- 178 01111105 4. 63 3,4,5-trimethoxyphenyl. 144 CwHmOa 4. 56 2,4,5-trimethoxypheny1. 210 019111000 4. 77 KIA-methylene dioxyphenyl- 226 (311111001 3. 33 3-chlorophenyl 224 CmHvClQ-i 3. 21 4-chlorophenyl- 203 CmI-IqClOa 3. 04 4-br0mophenyl 204 CmHnBrOa 2. 66 3-indo1yl-.-.- 308 CisHnNo 3. 94 2-naphthyl 251 020111203 4. 01 l-naphth yl 184 020131203 3. 95 n-Propy 58 013111203 5. 44

hydrofuran, dioxane; and the like. A lO-fold to 5000-fold EXAMPLE 2 molar excess of fluorogen is preferred. A 50-fold to 1000- a fold molar excess is especially preferred.

Alternatively, the fluorogens of the present invention may be utilized to detect the presence of primary aminecontaining compounds, especially amino acids, on paper or thin-layer chromatographic systems. In such a technique, the reagent in a solvent, preferably a volatile organic solvent, optionally containing a pH butter, is ap- To a solution of 20 g. of 3-benzylidene-4-keto-3,4-dihydroisocoumarin in 400 ml. methanol were added ml. 1 N aqueous sodium hydroxide. The mixture was stirred at room temperature for 30 minutes. It was then diluted with water and acidified with 10% hydrochloric acid. The precipitating o-(a hydroxycinnamoyl) benzoic acid was extracted twice with chloroform. The organic extracts were plied to the chromatographic system, usually as a spray, 75 washed with water, dried over sodium sulfate and evaporated under reduced pressure to dryness. The residue was dissolved in 80 ml. dimethylformamide. The solution was s deneor 3-a1kylidene-4-keto-3,4-dihydroisocoumarins, prepared as in Example 1.

TABLE II Analysis Calcd Found M.P., Empirical R: degree formula C H N O H N 2-methoxypheny1 153 O1sH120 70.13 3. 92 70.24 3. 86 3-methoxyphenyL. 118 01 111201 70.13 3. 92 70.13 3.71 4-methoxypheny 158 013111205 70.13 3. 92 70.40 4.01 2,4-dimet oxyphenyl. 133 019111401 67.45 4.17 67.21 4.06 2,5-dirnethoxyphenyL 148 CnHMQa 67.45 4.17 67.54 4. 09 3,5-dimethoxypheny1 138 CwHuOa 67. 45 4. 17 67. 72 3. 98 3,4,5-trimethoxyphenyl- 205 CzqHmOz 65. 21 4. 38 65. 33 4. 26 2,4,5-trimeth0xyphenyl 179 02 111101 65.21 4.38 65.34 4.27 3,4methylenedioxyphenyl 195 011111 01 67.08 3.13 67.08 3.43 3-chlorophenyl 144 C1 HqClO4 65. 30 2. 90 65. 32 2. 61 4-ch1oropheny1- 167 C11H9Cl04 65. 3O 2. 90 65. 10 2. 92 4-br0mophenyL 181 C17H0BIO4 57.17 2. 54 57.25 2. 63 3-indolyl 186 CwH11NO4 71.92 3.49 72.16 3.43 2-naphthy1 170 021111204 76. 82 3. 68 76. 62 3. 58 l-naphthyl. 191 C21Hr204 76. 82 3. 68 76 85 3. 53 n-Propyl Oil (314111204 cooled to 0, and, while stirring, 24 ml. tris(dimethylamino)methane were added. Stirring was continued at room temperature for 60 minutes. The l-dimethylamino- 2-phenyl-4(o-carboxyphenyl)-l-buten 3,4 dione which had formed was not isolated, but rather, the DMF-solution was poured into ice-water. The resultant aqueous alkaline solution was extracted with ether. The ether extract was discarded and the aqueous layer was acidified with dilute hydrochloric acid. The desired 4-phenylspiro [furan-2(3H)-l-phthalan]3,3-dione was extracted three times with ether/benzene (1:1). The combined extracts were dried over sodium sulfate and evaporated under reduced pressure. The crystalline residue was resuspended in ether and filtered off to give 12.0 g. pure material, M.P. 153.

Analysis.--Calcd. for C H O C, 73.38; H, 3.62. Found: C, 73.41; H, 3.57.

The compounds listed in Table II were prepared by analogous procedures, starting with the appropriate 3-aryli- EXAMPLE 3 To a suspension of 2.5 g. 3-benzylidene-4-keto-3,4-dihydroisocoumarin in 50 ml. methanol were added 10 ml. of l N aqueous sodium hydroxide. The mixture was stirred at room temperature for 1 hour. A dark red solution resulted. The solution was diluted with water, acidified with 10 ml. of 1 N hydrochloric acid and extracted three times with methylene chloride. The organic extracts were combined, washed with water, dried over sodium sulfate, and evaporated in vacuo at 20-30". The residue was dissolved in methylene chloride at room temperature. Petroleum TABLE III Analysis Calcd Found I M.P., Empirical R: degree formula C H N C H N 2methoxyphenyl 131-136 O11H14O5 68.45 4.73 3-n1ethoxyphenyL. 133-435 011111405 68.45 4.73 4-Inethoxyphenyl 117-123 011111405 68.45 4.73 2,5-d1methoxypheny 131132 CmHmOu 65.85 4.91 3,5-dlrnethoxyphenyl. 131-134 Oral-1100a 65.85 4.91 2,4,5-trimethoxyphen 152-165 019111101 63.68 5.06 3-chl0rophenyl 117-118 CwHuClO4 63.48 3.66 4-bromophen 130-132 OwHnBrOi 55.35 3.19 3-1ndo1yl -125 CrsHraNOM/ 63.52 4.03 l-naphthyL 154460 020111404 .46 4.43

9 EXAMPLE 4 To a solution of 268 mg. (a hydroxycinnamoyl) benzoic acid in ml. of dimethylformamide were added 2 ml. dimethylformamide dimethyl acetal. The reaction mixture was kept at room temperature for 17 hours. The solution containing 1 dimethylamino-2-pheuyl-4(o-carboxyphenyl)-1-buten-3,4dione was then poured into water, acidified with dilute hydrochloric acid and extracted with methylene chloride. The organic extract was dried over sodium sulfate and concentrated in vacuo. The concentrate was applied to a short silica gel column (4.5 g.) and eluted with methylene chloride. The eluate was evaporated in vacuo and the residue was recrystallized from methylene chloride/ether. There were obtained 110 mg. 4-phenylspiro [furan-2(3H) 1-phthalan]3,3 dione, M.P. 151-154".

EXAMPLE 5 To a solution of 12.5 g. 3-benzylidene-4-keto-3,4-dihydroisocournarin in 200 ml. methanol were added 50 ml. of 1 N aqueous sodium hydroxide. The reaction mixture was stirred at room temperature for 90 minutes. It was then poured onto ice. The resulting aqueous mixture was acidified with 50 ml. of 1 N hydrochloric acid and extracted 4 times with methylene chloride. The extracts were combined, dried over sodium sulfate and evaporated in vacuo. The residue containing o-(ot-hydroxycinnamoyl) benzoic acid was dissolved in 150 ml. dimethylformamide. To this solution were added 30 g. tris-(piperidino)methane. The mixture was stirred at room temperature for 5 hours and the solution containing 1 (1 piperidino)-2- phenyl 4 (o carboxyphenyl)-1-buten-3,4-dione then poured into ice-water. The alkaline aqueous mixture was extracted with ether. The ether extract was discarded. The aqueous layer was acidified with 1 N hydrochloric acid (300 ml.) and extracted four times with methylene chloride. The organic extracts were combined, washed with water, dried over sodium sulfate and evaporated to dryness under reduced pressure. The residue was dissolved in 75 ml. methylene chloride and treated with 1 g. of Norite at reflux temperature. The hot solution was filtered. The filtrate was concentrated to 50 ml. and then diluted with 100 ml. ether. From the mixture there crystallized 8.4 g. of 4 phenylspiro [furan-2(3H),1'-phthalan] 3,3-dione; M.P. 151-153".

The compounds listed in Table II were prepared by analogous procedures, starting with the appropriate 3- arylideneor 3-alkylidene-4-keto-3,4-dihydroisocoumarins prepared as in Example 1.

EXAMPLE 6 To a solution of 4.47 g. o-(a-hydroxy-2-methoxycinnamoyl) benzoic acid in 30 ml. dimethylformamide were added. 5 g. tris-(dimethylamino)-methane. The mixture was stirred at room temperature for 3 /1 hours. Most of the excess formylating agent and the solvent were thenremoved under reduced pressure at 55-60. The residue containing 1 dimethylamino-2-(o-methoxyphenyl)-4-(ocarboxyphenyl)1-buten-3,4-dione was redissolved in 10 ml. of dimethylformamide and this solution added to 100 ml. water. The resulting alkaline mixture was extracted with methylene chloride. The organic extract was discarded. The aqueous layer was acidified with dilute hydrochloric acid and extracted twice with methylene chloride. The organic phases were combined, washed with water, dried over soduim sulfate and evaporated to dryness under reduced pressure. The remaining oil was dissolved in ether. Crystals precipitated from the ether solution upon refrigeration. They were collected by filtration to afford 2.4 g. 4-(2-methoxyphenyl)spiro[furan-2(3H), 1"-phthalan]-3,3'-dione, M.P. 152-154".

The compounds listed in Table III were converted to the corresponding spirolactones listed in Table II by analogous procedures.

10 EXAMPLE 7 Fluorometric assay Procedure: Place in a test tube:

(a) 1 m1. of peptide solution (20 nanomole leucyl-alanine in 1 ml. pH 8-phosphate buffer) and (b) 2 ml. pH 8-butfer solution (Fisher). While agitating with a vibro-mixer add rapidly:

(c) 1 m1. of reagent solution (containing 0.2 millimole of spirolactone of Table II in 100 ml. acetonitrile).

Final concentrations:

Leu-ala: 5 nanomole/ml.

reagent: 0.5 pimole/ml. (100 fold excess) acetonitrile: 25%

aqueous buffer:

Measure fluorescence immediately.

Instrumention:

Farrand Spectrofluorometer Excitation: 390 nm.; slits 10,10 Emission: 385 nm.; slits 20,20 Sensitivity=1 Results: With 4-phenylspiro[furan-2(3H),1'-phthalan] 3,3'-dione as the reagent a fluorescent intensity of 80, relative to a fluorescence intensity of 70 (at the same excitation and emission settings) for a quinine standard, 10 mg./ml. of 0.01 N H was observed.

The above experiment was repeated using ethylamine in place of leucylalanine, and ethanol in place of acetonitrile. The fluorescence intensity obtained by utilizing various spirolactone reagents of Table II is shown in Table IV. The fluorescence intensity obtained using 4-phenylspiro[furan-2(3H),1-phthalan]3,3 '-dione has been arbitrarily assigned the value 100, and the other intensities are given relative to it.

TABLE IV rescence Compound 0! Table II, R= Ex. Em. intensity Phenyl 390 475 3'methoxyphenyl" 391 475 -methoxyphenyl- 395 495 110 3,5-dimethoxyphenyl. 390 475 4-eh1orophenyl 390 475 110 l-naphthyl 310 483 94 3,4,5trlmethoxypheny 390 475 60 nropyl 370 445 47 EXAMPLE 8 Starting with the appropriate S-substituted 2 acetylbenzoic acids, and proceeding, first according to known procedures, to the corresponding 7 substituted-1,4-isochromandione, and then, according to the procedure of Example 1, to the 7-substituted-3-benzylidene-4-keto-3,4- dihydroisocoumarin, the following series of intermediates and fluorogens were prepared, following the procedures of Example 2:

1 1 5'-methoXy-4-phenylspiro [furan-Z (3H) ,1'-phthalan]- 3,3 -dione, 3-benzylidene-4-keto-7-chloro-3 ,4-dihydroisocoumarin, 2- (a-hydroxycinnamoyl) -5-ch1oro-benzoic acid, l-dimethylamino-Z-phenyl-4 2-carboxy-4-chlorophenyl)-1-buten-3 ,4-dione, 5 '-chloro-4-phenylspir0 [furan-2(3H) 1'-phthalan] 3,3 '-dione.

We claim: 1. A compound of the formula COzH 0 00211 O 12 group consisting of phenyl and naphthyl, which radical may be unsubstituted or substituted with one or more halogen, lower alkyl, lower alkoxy, nitro or cyano groups. 2. The compound of claim 1 wherein R is hydrogen. 3. The compound of claim 2 which is o-(or-hydroxycinnamoyl)benzoic acid.

References Cited Newman et al.: Jour. Amer. Chem. Soc., vol. 67 (1945), pp. 233-7.

Bennett: Trans. Faraday Soc. (1941), pp. 794-804.

JAMES A. PATTEN, Primary Examiner U.S. Cl. X.R.

23230 M; 260240 R, 240 F, 251 R, 287 R, 295 SP, 307 R, 309, 332.2 H, 340.5 343.3, 326.13 R, 515 R, 515 A, 518 R, 518 A, 519 

